How do I remove the line from the camera view?
That line is the camera object itself. Either its width is very small or its height is very large, which is making it display as a line. The camera gets its size from the Resolution and Aspect Ratio properties in the Dimensions panel in the Render tab of the Properties editor:



Set your resolution to something more regular (or pick a Render Preset from the drop-down box) and make sure your Aspect Ratio is '1' for both x and y.